The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Controllers for disk drives often include a read/write component, which is typically referred to as a read channel (RDC). The RDC is responsible for reading data from the physical disk medium and for writing data to the disk medium, and acts as an interface to other components of the hard disk controller. The RDC and other components of the hard disk controller pass data among themselves over a parallel data bus, which is often referred to as a non-return-to-zero (NRZ) bus.
Disk drives and disk drive controllers are typically tested during or after manufacture to confirm proper operation. During such testing, an external tester can be connected to the parallel NRZ bus of the disk controller to provide data and commands and to receive data that is read from the disk medium. With the increasing data transfer speeds of hard disks, however, it has become difficult to maintain sufficient bus speeds between the disk controller and the external testing equipment.